1. Field of the Invention
This invention pertains to devices used to lift concrete building or retaining wall blocks into position on a wall, and more particularly, to such devices that enable several pairs of blocks to be simultaneously lifted from their original positions on a pallet and shifted to varied positions on a wall.
2. Description of the Related Art
Lifting devices that are attachable to backhoes to help construction workers more efficiently set concrete blocks in place on building or retaining walls are widely known. These devices eliminate the need for workers to individually lift and position the heavy concrete blocks, saving time, physical energy, and labor cost. Unfortunately, such devices are able to lift and position only one concrete block at a time, which makes wall building a slow, tedious process.
Retaining wall blocks are shipped from the manufacturer on pallets. Typically, the pallets 95, 96 come in two sizes: 3xe2x80x2xc3x973xe2x80x2 and 3xe2x80x2xc3x974xe2x80x2, as shown in FIGS. 7 and 8, respectively. The 3xe2x80x2xc3x973xe2x80x2 pallet 95 has four pairs of blocks, while the 3xe2x80x2xc3x974xe2x80x2 pallet 96 has six pairs of blocks. Each block in a pair of blocks is longitudinally aligned in an end-to-end orientation with the other. Each pair of blocks is longitudinally aligned in rows.
In order to expedite the process and reduce labor and rental equipment costs, what is needed is a lifting device that allows a backhoe operator to easily and securely lift multiple pairs of concrete blocks directly off the pallet and then adjust their relative positions for direct placement on a retaining wall.
It is an object of the present invention to provide a device for lifting a plurality of blocks from a pallet and position them on a retaining wall.
It is another object of the present invention to provide such a device that lifts the concrete blocks from their original positions on a shipping pallet.
It is a further object of the invention to provide such a device that lifts blocks that are positioned in rows and aligned in an end-to-end manner with an adjacent block on a pallet.
These and other objects of the invention which will become apparent are met by the lifting device disclosed herein that includes two horizontal support arms, each with a plurality of block attachment units mounted on the arm""s outside surface and designed to attach to blocks in their original locations on a pallet, securely lift them and place them on a retaining wall. The support arms are pivotally connected at their ends and move between a closed, parallel configuration to an open, linear configuration. A means for controlling the pivotal movement of the support arms, such as central hydraulic cylinder, is disposed between the two support arms, and used to selectively control their movements between the two configurations.
Each block attachment unit includes a downward extending sleeve member designed to slide freely into a hole formed on a block. Located inside the sleeve member is hole engaging member that selectively engages the sides of the hole to temporarily attach the block attachment unit to the block. In one embodiment, the hole engaging member is an actuator arm that moves longitudinally inside the sleeve member and moves a gripping member between engaged and disengaged positions against the inside surface of the hole. Each actuator arm is connected to a hydraulic cylinder that connects to a main control valve mounted on the device that controls the operation of the hydraulic cylinders used to control the block attachment units and the movement of the support arms.
Fixed to each arm is a lifting bracket which connects to a chain or cable suspended from a backhoe which is used to lift the lifting device in a horizontal orientation over the pallet or wall.
In the first embodiment, the lifting device includes two block attachment units evenly spaced apart on each arm at selected distances so that four pairs of blocks placed in rows facing each other may be lifted. During use, the support arms are initially positioned in the closed, parallel configuration and lowered over the four blocks. After each sleeve member on each block attachment unit is inserted into a central hole on a block, the hydraulic cylinder on each block attachment unit is activated to move the actuator arm and to force the gripping member outward against the inside surface of the hole, applying sufficient pressure to lift and hold each block. The lifting device is then raised so that the blocks clear the other remaining blocks on the pallet and allow the support arms to be moved into a linear configuration.
When the support arms are moved into a linear configuration the blocks are aligned side-by-side and face the same direction. The lifting device is then properly positioned over the wall and lowered to properly position the blocks on the wall. The hydraulic cylinder on each block attachment unit is then deactivated to release the actuator arm and disengage the gripping member from the sides of the hole. The lifting device is then raised so that the sleeve members clear the holes and the central hydraulic cylinder is activated to realign the support arms in a closed, parallel configuration. The lifting device is then repositioned over the pallet to attach to four more pairs of blocks.